Transcript Document

The Internet Book
Chapter 15
Communication Protocol
• A common language
computers use to
exchange messages.
–Specifying exact format
and meaning of each
message
–Sending and receiving
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Basic Functionality: Internet
Protocol (IP)
• IP defines computer
communication details.
–Specifying how packets are formed
–Specifying how routers forward each
packet
• Computers connecting to the
Internet must follow the IP rules.
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IP Software On Every Machine
• Computer hardware does not
understand IP.
–Connecting a computer to the
Internet does not mean it can use
the Internet
• Computers need IP software
before using the Internet.
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Internet Packets Are Called
Datagrams
• IP Datagrams are
packets that follow the
IP specifications.
– Traveling across the
Internet independent of
sender
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The Illusion Of A Giant
Network
• Any computer can send IP
datagrams to any other computer
providing they have IP software
installed.
• The Internet operates like a virtual
network.
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Figure 15.1
Figure 15.1 The view of the Internet that IP software provides. Users and application
programs treat the Internet like a single large network that allow arbitrary numbers of
computers to communicate.
The Reality Of Internal
Structure
• The Internet contains a complex
physical structure users never
see
–Interconnecting networks with
routers
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Figure 15.2 A small example of the physical structure that remains hidden inside the Internet. Each computer
attaches to a single network; routers interconnect the networks.
Figure 15.2
Datagrams Travel In Packets
• IP datagram defines a standard for
all Internet packets. Routers:
–Encloses the data before sending
out the packet
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Every Computer Is Assigned A
Unique Address
• Each computer attached to the
Internet must be assigned a
unique address.
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Internet Addresses
• The unique number assigned to
a computer is its Internet (IP)
address.
• Each computer (including
routers) need to have an IP
address.
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An Odd IP Address Syntax
• Computer stores IP address in
four binary units called bytes.
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IP Addresses Are Not Random
• IP addresses are not random.
• Computers on the same
network have the same prefix.
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A Trip Through The Internet
• A router must choose between
two paths that both lead to the
destination.
–Choosing the shortest path
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Figure 15.3
Figure 15.3 An example of internet with six networks and three computers attached.
Conclusion
• Why is it important to have the
Internet protocol scheme?
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Glossary
• Protocol
•
•
– The rules two or more computers must
follow to exchange messages
Internet Protocol
– (IP) Specification for the format of
packets computers use when
communicating across the Internet
IP Datagram
– A packet of data sent across the Internet
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Glossary
• Virtual Network
•
– Appearance of a single, seamless
network system
Internet Address
– (IP Address) An unique number
assigned to a computer attached to
the Internet
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